You used a function “wait” all lower case which is not an EasyC function. Replace all instances of that with “Wait” (uppercase W) and it will compile without the link errors.
Word of advice, always post in the public forums and you will get a quicker reply than the “official” forums where most of us cannot reply.
Edit: I should add that the link errors are caused because wait() is in fact a C function that is used to wait for a child process (usually created by the function fork() ) to terminate. The compiler knew something about this and tried to find everything in the standard libraries, they presumably don’t exist in the EasyC release.